The color and intensity of the light given off from photoluminescent porous silicon can be modified by chemical adsorbates. For example, when porous silicon is exposed to vapors of the carcinogen benzene, its luminescence intensity drops by more than 50%. The effect is reversible, so when the chemical evaporates off, the original intensity of the luminescence is recovered. A variety of polyaromatic hydrocarbons affect porous silicon in a similar fashion. This property demonstrates the feasibility of using porous Si in gas or liquid sensors. The students involved in the proposed project will quantify the response of porous silicon toward polyaromatic hydrocarbons, carbon monoxide, nitric oxide, carbon dioxide, and heavy metals, in order to define the potential for this material to act as a sensor for these biologically relevant chemicals.